Immersion deposition of Ni on P-Si (100) blank substrates was carried out in an aqueous NiSO4 solution at a pH value of 8 through displacement reactions. Study of the early deposition stage revealed that incorporation of 2.5 M NH4F in solution promoted Ni nucleation significantly. By adding fluoride, it was observed that metallic Ni was deposited constantly at the expense of Si and the deposition was not selflimited. Sponge-like Ni deposits were observed and it might explain the non-limiting feature of such immersion Ni deposition over Si. Transmission electron microscopic images of Ni/Si cross-sections showed that during the reactions, Si oxide played a role of the intermediate phase. The whole process could have involved successive Si oxidation steps. Eventually the oxide was etched away by fluoride resulting in a nanoporous Ni film. (c) 2006 Elsevier B.V. All rights reserved.